The name granny is given in Vocabulary of Sea Phrases (Anonymous, 1799) and Roding pictures the knot in 1795.

The granny consists of two identical half knots, one tied on top of the other.

Formerly it was employed for tying up parcels in five-and-ten-cent stores, but the practice was given up and paper bags substituted as they were found to be simpler.

The granny knot is the first step repeated twice, left over right, tuck under.

This is a very common mistake made by people learning to tie a reef knot.